Image capturing apparatus, method of controlling the same, and storage medium

ABSTRACT

An image capturing apparatus comprises an imaging unit, a sensor unit, a first focus detection unit configured to detect a first in-focus position based on a pair of image signals, a second focus detection unit configured to detect a second in-focus position based on a signal output from the imaging unit, a control unit configured to control a position of the focus lens and control display indicating the focus detection areas, and a correction unit configured to acquire a correction amount for correcting the first in-focus position, wherein the correction unit determines a first focus detection area from which the correction amount is to be acquired while the focus lens is moved to the second in-focus position, and wherein the control unit controls the first focus detection area to be identifiable.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a technique of correcting the in-focusposition obtained by a phase difference detection method based on thein-focus position detected by a contrast detection method.

Description of the Related Art

Conventionally, there is known a technique of performing focus detectionby the phase difference detection method of detecting the focus state(defocus amount) of an imaging optical system from the phase differencebetween a pair of images formed by light passing through the imagingoptical system in an interchangeable lens in a lens-interchangeableimage capturing apparatus such as a single-lens reflex camera. Such aphase difference detection method has a problem that an in-focusposition may not be accurately detected due to the influences of a lightsource, the color or the type of an object, or the like at the time ofimaging.

In order to solve such a problem, Japanese Patent Laid-Open No.2003-295047 discloses a camera having a focus calibration function forcorrecting the in-focus position obtained by the phase differencedetection method based on the in-focus position detected by the contrastdetection method. In the contrast detection method, a focus evaluationvalue indicating the contrast of an object is obtained from the videosignal generated by using the image sensor of a digital camera, and theposition of a focus lens where the focus evaluation value is maximizedis set as an in-focus position. When detecting a position where amaximum focus evaluation value is obtained, changes in focus evaluationvalue are monitored while the focus lens is finely driven. The digitalcamera disclosed in Japanese Patent Laid-Open No. 2003-295047 correctsthe in-focus position obtained by the phase difference detection methodat the time of imaging by using the correction value obtained by focuscalibration, and moves the focus lens to the in-focus position after thecorrection, thereby performing more accurate in-focus control.

In addition, according to Japanese Patent Laid-Open No. 2007-041095, thepseudo-object image generated inside a camera is displayed on anexternal display device, and an in-focus position is obtained withrespect to the pseudo-object image by each detection method in the focuscalibration mode. Disclosed is a camera which corrects the in-focusposition obtained by the phase difference detection method from thedetection result.

Recently, in a focus detection apparatus based on the phase differencedetection method, as a focus detection area increases with respect to animaging field angle in accordance with user's requirements, the numberof detection points increase. This makes it necessary to consider afocus calibration method in accordance with a focus detection apparatusbased on the phase difference detection method which is mounted in animage capturing apparatus.

However, the related art disclosed in Japanese Patent Laid-Open No.2003-295047 described above makes no reference to focus calibrationmethods or display methods corresponding to different detection areas ordetection point counts. In addition, the above related art only mentionsthat, with regard to an object used for in-focus position detection atthe time of calibration, it is preferable to use, for accurate focuscalibration, a dedicated chart rather than a general object.

According to the related art disclosed in Japanese Patent Laid-Open No.2007-041095, in order to perform focus calibration, it is necessary todisplay a dedicated chart (pseudo-object image) on an external displaydevice. For this reason, even if a user needs to perform focuscalibration in a field, he/she cannot perform focus calibration withoutany external display apparatus.

SUMMARY OF THE INVENTION

The present invention has been made in consideration of the aboveproblem, and makes it possible to perform a focus calibration of a focusdetection of a phase difference method using a general object withoutusing a dedicated chart.

According to the first aspect of the present invention, there isprovided an image capturing apparatus comprising: an imaging unitconfigured to generate an imaging signal by photoelectrically convertingan object image formed by an imaging optical system including a focuslens; a sensor unit including a plurality of pairs of sensors each ofwhich generate a pair of image signals by photoelectrically convertingan object image formed by the imaging optical system in correspondencewith each of a plurality of focus detection areas; a first focusdetection unit configured to detect a first in-focus position based onthe pair of image signals generated by the sensor unit; a second focusdetection unit configured to detect a second in-focus position based ona signal output from the imaging unit; a control unit configured tocontrol a position of the focus lens and control display indicating thefocus detection areas; and a correction unit configured to acquire acorrection amount for correcting the first in-focus position at the timeof imaging based on a difference between the first in-focus position andthe second in-focus position in a correction mode, wherein in thecorrection mode, the correction unit determines a first focus detectionarea, among the plurality of focus detection areas, from which thecorrection amount is configured to be acquired while the focus lens ismoved to the second in-focus position by the control unit, and whereinthe control unit controls display indicating the first focus detectionarea determined by the correction unit to be identifiable.

According to the second aspect of the present invention, there isprovided an image capturing apparatus comprising: an imaging unitconfigured to generate an imaging signal by photoelectrically convertingan object image formed by an imaging optical system including a focuslens; a sensor unit including a plurality of pairs of sensors each ofwhich generate a pair of image signals by photoelectrically convertingan object image formed by the imaging optical system in correspondencewith each of a plurality of focus detection areas; a first focusdetection unit configured to detect a first in-focus position based onthe pair of image signals generated by the sensor unit; a second focusdetection unit configured to detect a second in-focus position based ona signal output from the imaging unit; a control unit configured tocontrol a position of the focus lens and control display indicating thefocus detection areas; and a correction unit configured to acquire acorrection amount for correcting the first in-focus position at the timeof imaging based on a difference between the first in-focus position andthe second in-focus position in a correction mode, wherein in thecorrection mode, the control unit performs control to identifiablydisplay information indicating whether the correction amount isconfigured to be acquired with respect to each of the plurality of focusdetection areas, while the focus lens is moved to the second in-focusposition, and wherein the correction unit acquires the correction amountwith respect to the focus detection area displayed in a first formindicating that the correction amount is configured to be acquired,whereas the correction unit limits acquisition of the correction amountwith respect to the focus detection area displayed in a second formdifferent from the first form.

According to the third aspect of the present invention, there isprovided a method of controlling an image capturing apparatus includingan imaging unit configured to generate an imaging signal byphotoelectrically converting an object image formed by an imagingoptical system including a focus lens, and a sensor unit including aplurality of pairs of sensors each of which generate a pair of imagesignals by photoelectrically converting an object image formed by theimaging optical system in correspondence with each of a plurality offocus detection areas, the method comprising: a first focus detectionstep of detecting a first in-focus position based on the pair of imagesignals generated by the sensor unit; a second focus detection step ofdetecting a second in-focus position based on a signal output from theimaging unit; a focus control step of controlling a position of thefocus lens; a display control step of controlling display indicating thefocus detection areas; and a correction step of acquiring a correctionamount for correcting the first in-focus position at the time of imagingbased on a difference between the first in-focus position and the secondin-focus position in a correction mode, wherein in the correction mode,while the focus lens is moved to the second in-focus position in thefocus control step, a first focus detection area, among the plurality offocus detection areas, from which the correction amount is configured tobe acquired is determined in the correction step, and wherein in thedisplay control step, display indicating the first focus detection areadetermined in the correction step is controlled to be identifiable.

Further features of the present invention will become apparent from thefollowing description of exemplary embodiments with reference to theattached drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view showing the arrangement of a digitalsingle-lens reflex camera (in a mirror-down state) according to thefirst embodiment of the present invention;

FIG. 2 is a sectional view showing the arrangement of the digitalsingle-lens reflex camera (in a mirror-up/live view state) according tothe first embodiment;

FIG. 3 is a block diagram showing the electrical arrangement of thedigital single-lens reflex camera according to the first embodiment;

FIG. 4 is a flowchart showing a focus calibration operation in the firstembodiment;

FIG. 5 is a flowchart showing an operation in a focus calibrationpossibility determination routine in the first embodiment;

FIG. 6 is a view showing a display state of a liquid crystal monitor inthe live view mode in the first embodiment;

FIG. 7 is a view showing focus calibration possibility determinationresult display in the first embodiment;

FIG. 8 is a flowchart showing a focus calibration operation in thesecond embodiment;

FIG. 9 is a flowchart showing an operation in a focus calibrationpossibility determination routine in the second embodiment;

FIG. 10 is a view showing a display state in a viewfinder in the secondembodiment;

FIG. 11 is a view showing focus calibration possibility determinationresult display in the second embodiment;

FIG. 12 is a flowchart showing a basic operation including an automaticfocus calibration function in the third embodiment;

FIG. 13 is a flowchart showing a focus calibration operation in thethird embodiment;

FIG. 14 is a flowchart showing a focus calibration operation in thefourth embodiment;

FIG. 15 is a view showing focus calibration possibility distancemeasurement point identification mode setting in the fourth embodiment;

FIG. 16 is a view showing data selection in focus calibrationpossibility distance measurement point identification display setting inthe fourth embodiment;

FIG. 17 is a view showing focus calibration possibility distancemeasurement point identification display setting in the fourthembodiment;

FIG. 18 is a view showing focus calibration execution count setting inindividual setting for focus calibration possibility distancemeasurement point identification display in the fourth embodiment;

FIG. 19 is a view showing display setting for distance measurementpoints where focus correction values can be acquired at the time offocus calibration in individual setting for focus calibrationpossibility distance measurement point identification display in thefourth embodiment;

FIG. 20 is a view showing display setting for distance measurementpoints where focus correction values cannot be acquired at the time offocus calibration in individual setting for focus calibrationpossibility distance measurement point identification display in thefourth embodiment;

FIG. 21 is a view showing limiting setting for distance measurementpoints where focus correction values are acquired at the time of focuscalibration in individual setting for focus calibration possibilitydistance measurement point identification display in the fourthembodiment;

FIG. 22 is a view showing individual setting confirmation in focuscalibration possibility distance measurement point identificationdisplay in the fourth embodiment;

FIG. 23 is a view showing an object in the first focus calibration andin-focus display at an AF frame position in the fourth embodiment;

FIG. 24 is a view showing AF frame identification display as the firstfocus calibration result in the fourth embodiment;

FIG. 25 is a view showing an object at the second focus calibration, anAF frame position, and AF frame display after the second focuscalibration result in the fourth embodiment;

FIG. 26 is a view showing an object at the third focus calibration, anAF frame position, and AF frame display after the third focuscalibration result in the fourth embodiment; and

FIG. 27 is a view showing an object at the fourth focus calibration, anAF frame position, and display on a liquid crystal monitor after focuscorrection values obtained by focus calibration with respect to alldistance measurement points are stored in the fourth embodiment.

DESCRIPTION OF THE EMBODIMENTS

The embodiments of the present invention will be described in detailbelow with reference to the accompanying drawings.

First Embodiment

FIGS. 1 and 2 are views showing the arrangement of a digital single-lensreflex camera as the first embodiment of an image capturing apparatus ofthe present invention.

Referring to FIGS. 1 and 2, a digital single-lens reflex camera body 1(to be referred to as a camera body) is shown. An interchangeable lens 3is detachably and interchangeably mounted on a mount 2 fixed on thecamera body 1. In addition, the mount 2 is provided with an interfaceunit (not shown) for communicating various types of signals with theinterchangeable lens 3 and supplying power from the camera body 1 to theinterchangeable lens 3.

The interchangeable lens 3 accommodates an imaging optical systemincluding a focus lens (focus element) 3 a, a variable magnificationlens 3 b, and a stop 19. Although FIGS. 1 and 2 show each lens as if itwere formed from one lens, each lens may be constituted by a pluralityof lenses.

In the camera body 1, a main mirror 4 formed from a half mirror canpivot between the down position shown in FIG. 1 and the up positionshown in FIG. 2. When observing the object image formed by the imagingoptical system through a viewfinder optical system to be described later(viewfinder observation state), the main mirror 4 pivots to the downposition where it is obliquely arranged in an imaging optical path asshown in FIG. 1. The main mirror 4 arranged at the down positionreflects a light beam from the imaging optical system and guides thelight to the viewfinder optical system. When performing imaging or liveview display (imaging/live view observation state), the main mirror 4pivots to the up position where it retracts from the imaging opticalpath as shown in FIG. 2. This guides a light beam from the imagingoptical system to a shutter 5 and an image sensor 6 (both of which willbe described later).

The shutter 5 controls exposure of the image sensor 6 to a light beamfrom the imaging optical system. The shutter 5 in this embodiment is afocal plane shutter and configured to close in the viewfinderobservation state and open in the imaging/live view observation state.

The image sensor 6 is constituted by a CCD or CMOS image sensor and itsperipheral circuit. The image sensor 6 photoelectrically converts anobject image and outputs the image-capturing signal. An image processingcircuit 54 to be described later (see FIG. 3) performs various types ofprocessing for the image capturing signal to generate an image signal.All the pixels are configured to independently output image capturingsignals. Some of the pixels serve as focus detection pixels, whichenables focus detection based on the phase difference detection methodat the image capturing plane (image capturing plane phase differenceAF). More specifically, the image sensor 6 includes a plurality of imagecapturing pixels each of which receives a light beam passing through theentire area of the exit pupil of the interchangeable lens 3 which formsan image of an object, thereby generating an image of the object. Theimage sensor 6 further includes a plurality of focus detection pixelseach of which receives a light beam passing through a partial area ofthe exit pupil of the interchangeable lens 3. The plurality of focusdetection pixels can receive light beams passing through the entireregion of the exit pupil of the interchangeable lens 3 as a whole. Thefocus detection pixels are discretely arranged in effective pixels toperform image capturing plane phase difference AF in the entire area ofthe image sensor 6. Image capturing plane phase difference AF has beendescribed in detail in Japanese Patent Laid-Open Nos. 2009-244429 and2010-117680, and hence a detailed description of it will be omitted.

A sub-mirror 7 which pivots together with the main mirror 4 reflects alight beam transmitted through the main mirror 4 and guides the lightbeam to an AF unit 8 to be described later when the main mirror 4 isarranged at the down position. The sub-mirror 7 pivots to the upposition together with the main mirror 4 in the imaging/live viewobservation state.

The AF unit 8 is constituted by a field lens 8 a arranged near an imageforming plane, a reflection mirror 8 b, a secondary image forming lens 8c, and an area sensor 8 d including a plurality of light-receivingelements arranged in a two-dimensional direction. The secondary imageforming lens 8 c forms a pair of object images from a light beamentering from the imaging optical system and reflected by the mainmirror 4, the sub-mirror 7, and the reflection mirror 8 b. The areasensor 8 d generates a pair of image signals by photoelectricallyconverting the pair of object images. The pair of image signals areoutput to a focus detection circuit 36 to be described later (see FIG.3). It is possible to detect the focus state of the imaging opticalsystem (that is, focus detection) by the phase difference detectionmethod. The secondary image forming lens 8 c is configured to form apair of object images with respect to each of objects included in aplurality of areas within the imaging frame. That is, a plurality offocus detection points (so-called distance measurement points) arearranged within the imaging frame. In this embodiment, 61 distancemeasurement points are arranged in this embodiment (see FIG. 7).

An object image is formed on a focus plate 9 by a light beam reflectedby the main mirror 4. A pentaprism 10 inverts the object image formed onthe exit plane of the focus plate 9 into an erect normal image. Aneyepiece lens 11 guides a light beam from the pentaprism 10 to an eye ofa user to make him/her observe the object image on the focus plate 9. Anoptical system constituted by the focus plate 9, the pentaprism 10, andthe eyepiece lens 11 is called a viewfinder optical system.

A display device 12 formed from a polymer dispersed liquid crystal panel(so-called PN liquid crystal panel) arranged near the focus plate 9inside the viewfinder optical system displays various types ofinformation such as 61 distance measurement points described aboveinside the viewfinder.

An RGB photometric sensor 13 formed from an image sensor such as a CMOSsensor or CCD can perform photometry of the luminance (so-called AE) ofan object image on the focus plate 9 and color measurement from an imagecapturing signal, face detection by generating an image from the imagecapturing signal, and the like in cooperation with a photometric opticalsystem (not shown).

A liquid crystal monitor 14 provided outside the camera body displaysimage signals (a live view image and a shot image) and various types ofinformation.

In the interchangeable lens 3, a focus motor 15 serves as a drive sourcewhich moves the focus lens 3 a in the optical axis direction. The focusmotor 15 rotates a lead screw 16. A rack mounted on the focus lens 3 a(mounted on a holding frame holding the focus lens 3 a in practice)meshes with the lead screw 16. For this reason, when the focus motor 15rotates the lead screw 16, the focus lens 3 a moves in the optical axisdirection as the lead screw 16 meshes with the rack.

A pulse plate 17 is mounted on the distal end of the lead screw 16 so asto be rotatable together with the lead screw 16. In addition, aphotocoupler 18 including a light-emitting element and a light-receivingelement which are arranged to sandwich part of the pulse plate 17 isarranged in the interchangeable lens 3. The photocoupler 18 generates apulse signal every time the light-receiving element receives light fromthe light-emitting element as the pulse plate 17 rotates. This pulsesignal is input to a focus adjustment circuit 34 to be described later(see FIG. 3). Counting the number of input pulse signals will detect themovement amount (or position) of the focus lens 3 a.

A stop driving unit 20 includes a stop driving circuit 35 to bedescribed later (see FIG. 3) and drives the stop 19 in the opening andclosing directions.

FIG. 3 is a block diagram showing the electrical arrangement of theabove digital single-lens reflex camera. A microcomputer (to be referredto as an MPU hereinafter) 30 is a main controller which controls thecamera body 1 and the overall camera system. A memory controller 31performs control concerning the operation of the image sensor 6 andimage data. An EEPROM 32 serving as a memory stores data for varioustypes of control.

A lens control circuit 33 provided in the interchangeable lens 3controls the focus adjustment circuit 34 and the stop driving circuit 35in the interchangeable lens 3 in accordance with signals from the MPU 30which are transmitted via the mount 2.

The focus adjustment circuit 34 receives information indicating thetarget movement amount of the focus lens 3 a from the lens controlcircuit 33, and also receives a pulse signal from the photocoupler 18(actual movement amount information indicating the actual movementamount of the focus lens 3 a). The focus adjustment circuit 34 drivesthe focus motor 15 to move the focus lens 3 a based on the targetmovement amount information and the actual movement amount information.The stop driving circuit 35 drives the stop 19 in accordance with a stopdriving signal from the lens control circuit 33.

The focus detection circuit 36 in the camera body 1 controls electriccharge accumulation and electric charge readout of the area sensor 8 dprovided in the AF unit 8 to output a pair of image signals obtained ineach focus detection area to the MPU 30. The MPU 30 calculates the phasedifference between a pair of input image signals by performingcorrelation computation with respect to the pair of image signals, andalso calculates a defocus amount indicating the focus state of theimaging optical system from the phase difference. The MPU 30 thencalculates the in-focus position of the focus lens 3 a based on opticaldata such as the defocus amount, the focal length of the imaging opticalsystem acquired from the interchangeable lens 3 (lens control circuit33), and the focus sensitivity of the focus lens 3 a. The in-focusposition (first in-focus position) obtained by the phase differencedetection method will be referred to as the phase difference in-focusposition in the following description. The MPU 30 transmits theinformation of the phase difference in-focus position to the lenscontrol circuit 33. The AF unit 8, the focus detection circuit 36, andthe MPU 30 constitute a focus control unit.

The lens control circuit 33 calculates a target movement amount for thefocus lens 3 a which is used to move the focus lens 3 a from the currentposition to the phase difference in-focus position, and outputs thetarget movement amount information to the focus adjustment circuit 34.As described above, with this operation, the focus adjustment circuit 34drives the focus motor 15 (not shown) and moves the focus lens 3 a tothe phase difference in-focus position. In this manner, focus detectionbased on the phase difference detection method and phase difference AFincluding focus adjustment are formed.

A photometric circuit 37 outputs a luminance signal from the RGBphotometric sensor 13 to the MPU 30. The MPU 30 A/D-converts theluminance signal into the photometric information of the object, andcomputes and sets an imaging exposure by using the photometricinformation. A series of operations from obtaining this photometricinformation to setting the imaging exposure will be referred to as AEoperation. Likewise, the color information of the object is obtainedfrom an RGB signal, and face detection is performed from an imagecapturing signal.

A motor driving circuit 38 controls a mirror motor (not shown) whichdrives the main mirror 4 and a charge motor (not shown) which chargesthe shutter 5. A shutter driving circuit 39 controls power supply to anelectromagnet (coil) (not shown) which holds the shutter 5 in a chargedstate.

A liquid crystal driving circuit 40 performs drive control on the PNliquid crystal panel 12 to display distance measurement points andvarious types of information in the viewfinder. A DC/DC converter 41converts the voltage of a power supply (battery) 42 into a voltagenecessary for each circuit in the camera body 1 and the interchangeablelens 3. The power supply 42 is detachable with respect to the camerabody 1.

A release button 43 is an operation member which is operated by the userto start imaging. Half-pressing (first stroke operation) the releasebutton 43 will turn on a first switch SW1 for starting imagingpreparation operations such as AE and AF. Fully pressing (second strokeoperation) the release button 43 will turn on a second switch SW2 forstarting exposure of the image sensor 6 for the generation of arecording image. ON signals from the first switch SW1 and the secondswitch SW2 are output to the MPU 30.

Operating a mode button 44 together with an electronic dial 45 makes itpossible to change the imaging mode in the camera body 1. An up/downcounter in the MPU 30 counts click signals corresponding to the rotatingoperation amount of the electronic dial 45. Various types of numericalvalues, data, and the like are selected in accordance with count values.

A multi-controller 46 is an operation input unit for selecting orsetting distance measurement points and details of various types ofimaging modes by making the user operate eight button portions providedon the upper, lower, left and right sides and between them.

A SET button 47 is an operation input unit for deciding selections andsettings made concerning distance measurement points, details of varioustypes of imaging modes, and various types of numerical values when theuser operates the mode button 44, the electronic dial 45, themulti-controller 46, and the like. When the user operates a power button48, the power supply of the camera body 1 (and the interchangeable lens3) is turned on/off.

A CDS (Correlation Double Sampling)/AGC (Automatic Gain Control) circuit50 performs sampling/holding and automatic gain control for the imagecapturing signal output from the image sensor 6. An A/D converter 51converts an analog output from the CDS/AGC circuit 50 into a digitalsignal. A TG (Timing Generation) circuit 52 supplies a drive timingsignal to the image sensor 6, a sample hold timing signal to the CDS/AGCcircuit 50, and a sample clock signal to the A/D converter 51.

The memory controller 31 detects the in-focus position of the focus lens3 a by the contrast detection method using the image capturing signaloutput from the image sensor 6 and output from the CDS/AGC circuit 50and the A/D converter 51. The in-focus position (second in-focusposition) detected by the contrast detection method will be referred toas a contrast in-focus position in the following description. The MPU 30performs focus calibration for correcting a phase difference in-focusposition based on the difference between the contrast in-focus positionand the phase difference in-focus position described above. The MPU 30and the memory controller 31 constitute a calibration unit.

In addition, the memory controller 31 performs the same processing asthat performed by the phase difference detection method calculated bythe MPU 30 using output signals from the focus detection pixels of theimage sensor 6, and detects the in-focus position of the focus lens 3 aby the image capturing plane phase difference detection method. Thein-focus position (third in-focus position) obtained by this imagecapturing plane phase difference detection method will be referred to asan image capturing plane phase difference in-focus position in thefollowing description.

An SDRAM 53 as a memory temporarily records data such as the imagedigitally converted by the A/D converter 51 and output signals from thefocus detection pixels of the image sensor 6. The image processingcircuit 54 generates image data for live view or recording by performingvarious types of processing such as Y/C (luminance signal/colordifference signal) separation, white balance correction, and γcorrection for the image capturing signal (digital signal) output fromthe A/D converter 51. The memory controller 31 can also obtain thephotometric information of the object (so-called image capturing planeAE) from the image data generated by the image processing circuit 54.

An image compression/decompression circuit 55 decompresses the imagedata obtained by compressing image data according to a format such asJPEG. A D/A converter 56 converts image data into an analog signal todisplay image data recorded in an SDRAM 53 or a recording medium 58 onthe liquid crystal monitor 14. An I/F (interface) 57 is an interfacewith the recording medium 58.

The operation of the digital single-lens reflex camera according to thisembodiment will be described next with reference to the flowcharts shownin FIGS. 4 and 5. The flowchart of FIG. 4 shows an operation performedin the normal calibration mode for focus calibration. The normalcalibration mode is a mode of simultaneously performing focuscalibration with respect to a plurality of distance measurement pointsat a given position of the focus lens 3 a. The MPU 30 and the memorycontroller 31, both of which are computers, execute the operations shownin FIGS. 4 and 5 in accordance with computer programs.

In step S101, the MPU 30 advances to step S102 when the user selects thenormal calibration mode by operating the mode button 44 and theelectronic dial 45.

In step S102, the MPU 30 starts live view (LV) display to perform focuscalibration. More specifically, the MPU 30 controls the mirror motor(not shown) via the motor driving circuit 38 to make the main mirror 4and the sub-mirror 7 pivot to the up position and retract outside theimaging optical path. In addition, the MPU 30 drives the charge motor(not shown) via the shutter driving circuit 39 to set the shutter 5 inan open state as shown in FIG. 2. The memory controller 31 then causesthe image sensor 6 to start photoelectric conversion (electric chargeaccumulation and electric charge readout), and causes the liquid crystalmonitor 14 to display the live view image as the moving image generatedby the image processing circuit 54 using the image capturing signal readout from the image sensor 6. The user searches for an object for focuscalibration while seeing this live view image, and arranges the camera.

FIG. 6 is a view showing the display state of the liquid crystal monitor14 in the live view mode. The liquid crystal monitor 14 is displaying atraffic sign 200 as a live view image. A TVAF frame 300 is displayed inthe center of the imaging screen. Although the TVAF frame 300 isarranged in the center of the imaging screen in FIG. 6, the TVAF frame300 may be arranged at any position on the imaging screen.

In step S103, the MPU 30 determines whether the user has half-pressedthe release button 43 to turn on the first switch SW1. If YES in stepS103, an object subjected to focus calibration is confirmed. The processthen advances to step S104. If NO in step S103, the process waits untilthe first switch SW1 is turned on.

In step S104, the MPU 30 drives the focus motor 15 via the lens controlcircuit 33 to start driving the focus lens 3 a in increments of apredetermined amount.

In step S105, the contrast in-focus position of the focus lens 3 a isdetected by the contrast detection method. More specifically, first ofall, the memory controller 31 reads out an image capturing signal in theTVAF frame 300 from the image sensor 6, and extracts a predeterminedfrequency component from the signal, thereby generating a contrastevaluation signal. The memory controller 31 then temporarily records thesignal in the SDRAM 53. The memory controller 31 determines whether animage exhibiting maximum (peak) contrast (to be referred to as a peakimage hereinafter) has been obtained. If a peak image can be detected,the process advances to step S106. If a peak image cannot be detected, apeak image is repeatedly detected at a position to which the focus lens3 a is driven by a predetermined amount. Since a peak image cannot bedetected unless at least three contrast evaluation images are acquired,step S105 is repeated at least three times.

In step S106, the MPU 30 stops the focus motor 15 via the lens controlcircuit 33 to finish driving the focus lens 3 a. At this time point, thefocus lens 3 a is at rest at a position (contrast in-focus position)where the traffic sign 200 as an object subjected to focus calibrationis in focus.

In step S107, 1 is set in a counter N for counting 61 distancemeasurement points of the area sensor 8 d. In step S108, the focuscalibration possibility determination routine is executed. A detailedoperation in this routine will be described later.

In step S109, it is determined whether the focus calibration possibilitydetermination routine has been executed with respect to the 61stdistance measurement point, that is, has been completed with respect toall the distance measurement points. If YES in step S109, the processadvances to step S111. If NO in step S109, the process advances to stepS110. In step S110, 1 is added to the counter N, and step S108 isrepeated.

In step S111, the memory controller 31 causes the liquid crystal monitor14 to display focus calibration possibility determination results on allthe distance measurement points of the area sensor 8 d. The focuscalibration possibility determination results can be discriminated byCAL_OK_FLAG or CAL_NG_FLAG temporarily recorded in the SDRAM 53 in thefocus calibration possibility determination routine described later.

FIG. 7 is a view showing a state in which focus calibration possibilitydetermination results are displayed on the liquid crystal monitor 14. AFframes 800 indicating 61 distance measurement points of the area sensor8 d are displayed. The individual numbers of the AF frames 800 arecounted from the left end to the right end, and from the upper side tothe lower side, starting from an AF frame 801 on the upper left, withthe central frame being an AF frame 831 and the lower right frame beingan AF frame 861. Therefore, the first distance measurement point of thecounter N corresponds to an AF frame 801, and the 61st distancemeasurement point corresponds to an AF frame 861. In addition, a CALstart button 310 and a cancel button 320 are displayed.

AF frames indicating distance measurement points where focus calibrationcan be performed are displayed in solid lines (801, 804, 814, 848, 858,861, and the like). AF frames indicating distance measurement pointswhere focus calibration cannot be performed are displayed in dottedlines (803, 831, 859, and the like) so as to be identifiable. Referringto FIG. 7, the focus calibration possibilities of the respectivedistance measurement points are indicated by the solid and dotted linesof AF frames (differences in line types or line widths). However, it ispossible to use any display method which allows the user to visuallydetermine possibilities, for example, by changing the display colors ofAF frames or displaying and hiding (or blinking) AF frames.

In step S112, the MPU 30 determines whether the user has turned on theCAL start button 310. More specifically, if the user operates the SETbutton 47 upon selecting the CAL start button 310 by operating theelectronic dial 45 or the multi-controller 46, the CAL start button isturned on, and the process advances to step S113. If the CAL startbutton 310 is not turned on (that is, the cancel button 320 is turnedon), the focus calibration mode is finished.

In step S113, the live view display is finished. More specifically, theMPU 30 controls the mirror motor (not shown) via the motor drivingcircuit 38 to make the main mirror 4 and the sub-mirror 7 pivot to thedown position shown in FIG. 2.

In step S114, the MPU 30 performs focus detection by the phasedifference detection method via the focus detection circuit 36 withrespect to a distance measurement point determined as a focuscalibration possible distance measurement point, and calculates a phasedifference in-focus position based on the result. The MPU 30 temporarilyrecords the position in the SDRAM 53.

In step S115, the MPU 30 calculates the difference between the contrastin-focus position obtained in step S105 and the phase differencein-focus position of the focus calibration possible distance measurementpoint obtained in step S114. This difference is a correction amount (tobe referred to as a CAL correction amount hereinafter) for the phasedifference in-focus position of the focus calibration possible distancemeasurement point.

In step S116, the MPU 30 records, in the EEPROM 32, the calculated CALcorrection amount for the focus calibration possible distancemeasurement point, and terminates the operation in the calibration mode.

The flowchart of FIG. 5 shows an operation performed in the focuscalibration possibility determination routine. This operation isperformed before or during focus calibration.

In step S151, the memory controller 31 reads out an image capturingsignal in an AF frame 8NN as the Nth distance measurement point from theimage sensor 6, and generates an evaluation image. In step S152, thememory controller 31 determines whether the contrast of the evaluationimage is equal to or more than a predetermined value. If the contrast isequal to or more than the predetermined value, the process advances tostep S153. If the contrast is less than the predetermined value, theprocess advances to step S157.

In step S153, it is determined whether the luminance of the evaluationimage falls within a predetermined range. If YES in step S153, theprocess advances to step S154. If NO in step S153, the process advancesto step S157.

In step S154, it is determined whether there are any objects exhibitingthe conflict of perspective in the evaluation image. If NO in step S154,the process advances to step S155. If YES in step S154, the processadvances to step S157.

In step S155, it is determined whether the evaluation image exhibits arepetitive pattern. If NO in step S155, the process advances to stepS156. If YES in step S155, the process advances to step S157.

If OK is determined in all four steps S152 to S155, accurate distancemeasurement can be done by phase difference AF in step S114. In stepS156, therefore, it is determined that focus calibration can beperformed with respect to the Nth distance measurement point. The MPU 30then temporarily records the result on the Nth distance measurementpoint (AF frame 8NN) as CAL_OK_FLAG in the SDRAM 53.

If NG is determined in any one of steps S152 to S155, phase differenceAF may result in a distance measurement error or incapability to performdistance measurement in step S114. In step S157, therefore, it isdetermined that focus calibration cannot be performed with respect tothe Nth distance measurement point. The MPU 30 then temporarily recordsthe result on the Nth distance measurement point (AF frame 8NN) asCAL_NG_FLAG in the SDRAM 53. The process then returns to step S109.

Referring to FIG. 7, since the object is the traffic sign 200, OK isdetermined concerning all the AF frames 801 to 861 in the threedeterminations (object determination): whether the luminance fallswithin the predetermined range, whether there are no objects exhibitingthe conflict of perspective, and whether the image is not a repetitivepattern. However, the contrast differs depending on the position of anAF frame arranged on the traffic sign 200. As described above, the AFframes 801, 804, 814, 848, 858, 861, and the like exhibit changes indesign inside the AF frames (include color switching edge lines). Forthis reason, the contrast of each AF frame becomes equal to or more thana predetermined value, and CAL_OK_FLAG is recorded. In contrast, the AFframes 803, 831, 859, and the like exhibit no changes in design insidethe AF frames (include no color switching edge lines). For this reason,the contrast of each AF frame becomes less than a predetermined value,and CAL_NG_FLAG is recorded.

Referring to FIG. 5, whether focus detection can be performed by thephase difference detection method is determined by the fourdetermination methods, that is, contrast determination, luminancedetermination, perspective conflict determination, and repetitivepattern determination using an image capturing signal from the imagesensor 6. However, it is possible to use any determination method whichcan determine an object from which it is difficult to obtain high focusdetection accuracy by the phase difference detection method. Forexample, it is possible to use a method using color determination or amethod based on determination of whether an in-focus state is obtainedby performing image capturing plane phase difference AF of the imagesensor 6.

As described above, according to this embodiment, whether focuscalibration can be performed with respect to the object selected by theuser is determined by using an image capturing signal from the imagesensor 6. This can prevent any wasteful correcting operation withrespect to an object from which sufficient focus calibration accuracycannot be obtained. Therefore, the user can easily and efficientlyperform focus calibration without using any dedicated chart.

Second Embodiment

The operation of a digital single-lens reflex camera according to thisembodiment will be described with reference to the flowcharts shown inFIGS. 8 and 9. The flowchart of FIG. 8 shows an operation performed in acalibration determination mode of determining whether focus calibrationcan be performed in a digital single-lens reflex camera system includingthe digital single-lens reflex camera according to the second embodimentof the present invention and an interchangeable lens. The arrangementsof the camera body and the interchangeable lens according to thisembodiment are the same as those in the first embodiment, and the samereference numerals as those in the first embodiment denote constituentelements common to those of the first embodiment. An MPU 30 and a memorycontroller 31, both of which are computers, execute the operations shownin FIGS. 8 and 9 in accordance with computer programs.

In step S201, when the MPU 30 detects that the user has selected thecalibration determination mode by operating a mode button 44 and anelectronic dial 45, the process advances to step S202. The calibrationdetermination mode in this embodiment is a mode performed on theviewfinder, and hence the user searches for an object subjected to focuscalibration while seeing the viewfinder.

In step S202, the MPU 30 determines whether the user has half-pressed arelease button 43 to turn on a first switch SW1. If YES in step S202, anobject subjected to focus calibration determination is confirmed. Theprocess then advances to step S203. If NO in step S202, the processwaits until the first switch SW1 is turned on.

In step S203, the MPU 30 focuses/drives a focus lens 3 a to the phasedifference in-focus position obtained by the phase difference detectionmethod. More specifically, the MPU 30 performs, via a focus detectioncircuit 36, focus detection by the phase difference detection method ata distance measurement point corresponding to a setting made in thecamera at this time. With regard to distance measurement pointssubjected to focus detection, if, for example, a distance measurementpoint selection mode is designed to select one arbitrary point, focusdetection is performed at the distance measurement point selected inadvance by the user, whereas if distance measurement points are to beautomatically selected, focus detection is performed at all the 61points. The MPU 30 decides a main distance measurement point based onthe focus detection result, lens information, and the like. The MPU 30then calculates a phase difference in-focus position based on the focusdetection result, and transmits the calculated information to a lenscontrol circuit 33. The lens control circuit 33 calculates the movementamount of the focus lens 3 a and drives the focus lens 3 a to the phasedifference in-focus position via a focus adjustment circuit 34.

In step S203, the MPU 30 performs focus detection by the phasedifference detection method via a focus detection circuit 36 withrespect to all the distance measurement points of an area sensor 8 d atthe stop position of the focus lens 3 a. The MPU 30 displays an AF frameindicating the distance measurement point in focus on a PN liquidcrystal panel 12 via a liquid crystal driving circuit 40 based on thefocus detection result.

FIG. 10 is a view showing a display state in the viewfinder. The objectimage formed on a focus plate 9 and various types of informationdisplayed on the PN liquid crystal panel 12 are currently displayedthrough a viewfinder optical system. The object whose image is formed onthe focus plate 9 is a building 210 having an electronic time board 211installed on the rooftop. AF frames 800 (801 to 803, 807 to 811, 816,824, 827, 831, 835, 838, 846, 849, 857, and the like) indicatingdistance measurement points in focus are displayed on the PN liquidcrystal panel 12.

In step S205, the MPU 30 counts the distance measurement points in focusand sets the count as a counter max value. Referring to FIG. 10, sincethe number of AF frames, of all the 61 distance measurement points,which are displayed in focus is 37, max=37.

In step S206, 1 is set in a counter M for counting distance measurementpoints subjected to focus calibration possibility determination. In stepS207, a focus calibration possibility determination routine is executed.The detailed operation in this routine will be described later.

In step S208, it is determined whether the focus calibration possibilitydetermination routine has been completed up to the distance measurementpoint corresponding to the counter max value. If YES in step S208, theprocess advances to step S210. If NO in step S208, the process advancesto step S209. In step S209, 1 is added to the counter M to repeat stepS207.

In step S210, the memory controller 31 displays focus calibrationpossibility determination results on the PN liquid crystal panel 12, andterminates the operation in the calibration determination mode. Thefocus calibration possibility determination results can be discriminatedby CAL_OK_FLAG or CAL_NG_FLAG temporarily recorded in an SDRAM 53 in thefocus calibration possibility determination routine described later.

FIG. 11 is a view showing a state in which focus calibration possibilitydetermination results are displayed on the PN liquid crystal panel 12.Out of the AF frames 800 displayed in focus in step S204, the AF frames802 and 806 to 811 whose focus calibration possibility determinationresults are NG are unlighted. The AF frames 801, 803, 807, 816, 824,827, 831, 835, 838, 846, 849, 857, and the like which are continuouslylighted indicate that focus calibration is possible. In addition, amessage 330 is displayed to allow the user to easily know that the focuscalibration possibility determination results are displayed.

Referring to FIG. 11, focus calibration possibility at each distancemeasurement point is indicated by lighting (displaying) or unlighting(hiding) the corresponding AF frame. However, it is possible to use anydisplay method which allows the user to visually determinepossibilities, for example, changing the display colors of AF frames ordisplaying AF frames in solid lines and dotted lines. In addition, thetext of message 330 is not limited to that in this embodiment, and anykind of text may be used. Furthermore, marks indicating focuscalibration possibilities may be displayed.

The flowchart of FIG. 9 shows an operation in the focus calibrationpossibility determination routine.

In step S251, the memory controller 31 reads out an image capturingsignal in an AF frame 8MM as the Mth distance measurement point from anRGB photometric sensor 13 via a photometric circuit 37, and generates anevaluation image.

In step S252, it is determined whether the contrast of the evaluationimage is equal to or more than a predetermined value. If the contrast isequal to or more than the predetermined value, the process advances tostep S253. If the contrast is less than the predetermined value, theprocess advances to step S256. In step S253, it is determined whetherthe luminance of the evaluation image falls within a predeterminedrange. If the luminance falls within the predetermined range, theprocess advances to step S254. If the luminance falls outside thepredetermined range, the process advances to step S256.

In step S254, it is determined whether the object is moving, by checkingwhether a signal representing the contrast or luminance of theevaluation image varies or fluctuates beyond a predetermined value ormore. If NO in step S254, the process advances to step S255. If YES instep S254, the process advances to step S256.

If OK is determined in all the three determinations in steps S252 toS254, accurate distance measurement can be performed by TVAF performedby an image sensor 6. In step S255, therefore, it is determined thatfocus calibration can be performed at the Mth distance measurementpoint. The MPU 30 then temporarily records the result on the Mthdistance measurement point (AF frame 8MM) as CAL_OK_FLAG in the SDRAM53.

If NG is determined in any one of the three determinations in steps S252to S254, TVAF performed by the image sensor 6 may result in a distancemeasurement error or incapability to perform distance measurement. Instep S256, therefore, it is determined that focus calibration cannot beperformed at the Mth distance measurement point. The MPU 30 thentemporarily records the result on the Mth distance measurement point (AFframe 8MM) as CAL_NG_FLAG in the SDRAM 53. The process then returns tostep S208.

Referring to FIG. 10, with regard to the AF frames set in focus by phasedifference AF (displayed on the PN liquid crystal panel 12), OK isdetermined in the two determinations, that is, whether the contrast isequal to more than a predetermined value and whether the luminance fallswithin a predetermined range. However, with regard to the AF frames 802and 808 to 811 on the electronic time board 211 as an object, since theobject is moving because of a change in the signal representing theevaluation image with the lapse of time during moving objectdetermination, it is determined that distance measurement cannot beperformed by TVAF. As a consequence, CAL_NG_FLAG is recorded. As aresult, as shown in FIG. 11, the AF frames 802 and 808 to 811 areunlighted, and only the AF frames where focus calibration can beperformed are displayed.

Referring to FIG. 9, whether focus detection can be performed by thecontrast detection method is determined by the three determinationmethods, that is, contrast determination, luminance determination, andmoving object determination using an image capturing signal from the RGBphotometric sensor 13. However, it is possible to use any determinationmethod which can determine an object from which it is difficult toobtain high focus detection accuracy by the contrast detection methodusing the image sensor 6, by using an image capturing signal from theRGB photometric sensor 13. For example, it is possible to use anydetermination method such as color determination for determining moreaccurate contrast values.

In addition, this embodiment has exemplified the mode of executing onlyfocus calibration possibility determination. However, as in the firstembodiment, it is possible to use the mode of executing focuscalibration after possibility determination.

As described above, according to this embodiment, whether focuscalibration can be performed with respect to the object selected by theuser is determined by using an image capturing signal from the RGBphotometric sensor 13. This can prevent any wasteful correctingoperation with respect to an object from which sufficient focuscalibration accuracy cannot be obtained. Therefore, the user can easilyand efficiently perform focus calibration.

Third Embodiment

The operation of a digital single-lens reflex camera according to thisembodiment will be described with reference to the flowcharts shown inFIGS. 12 and 13. The flowchart of FIG. 12 shows the basic operation ofthe digital single-lens reflex camera according to the third embodimentwhich has an automatic focus calibration function in a digitalsingle-lens reflex camera system including the digital single-lensreflex camera and an interchangeable lens. The arrangements of thecamera body and the interchangeable lens according to this embodimentare the same as those in the first embodiment, and the same referencenumerals as those in the first embodiment denote constituent elementscommon to those of the first embodiment. An MPU 30 and a memorycontroller 31, both of which are computers, execute the operations shownin FIGS. 12 and 13 in accordance with computer programs.

In step S301, the user selects an AF mode upon turning on the powersupply of the camera by operating a power button 48. If phase differenceAF is selected, the process advances to step S302. If TVAF is selected,the process advances to step S312.

In step S302, the MPU 30 determines whether the user has half-pressed arelease button 43 to turn on a first switch SW1. If YES in step S302, anobject is confirmed, and the process advances to step S303. If NO instep S302, the process waits until the first switch SW1 is turned on.

In step S303, the MPU 30 performs focus detection by the phasedifference detection method with respect to a distance measurement pointcorresponding to a setting in the camera at this time via a focusdetection circuit 36, and calculates a phase difference in-focusposition based on the detection result. The MPU 30 then temporarilyrecords the position in an SDRAM 53.

In step S304, the MPU 30 determines whether there is a CAL correctionamount for the distance measurement point where the phase differencein-focus position has been calculated. If YES in step S304, the processadvances to step S305. If NO in step S304, the process advances to stepS306.

In step S305, the MPU 30 reads out a CAL correction amount recorded inan EEPROM 32, and adds the amount to the phase difference in-focusposition temporarily recorded in the SDRAM 53. In step S306, the MPU 30transmits the phase difference in-focus position, to which the CALcorrection amount is added, to a lens control circuit 33. The lenscontrol circuit 33 then calculates the movement amount of a focus lens 3a, and drives the focus lens 3 a to the phase difference in-focusposition via a focus adjustment circuit 34.

In step S307, the MPU 30 determines whether the user has fully pressedthe release button 43 to turn on a second switch SW2. If YES in stepS307, the process advances step S308. If NO in step S307, the processwaits until the second switch SW2 is turned on.

In step S308, the MPU 30 shoots the object. More specifically, first ofall, the MPU 30 controls a mirror motor (not shown) via a motor drivingcircuit 38 to make a main mirror 4 and a sub-mirror 7 pivot to the upposition and retract outside the imaging optical path. The MPU 30 thendrives a charge motor (not shown) via a shutter driving circuit 39 tooperate a shutter 5 at a set shutter speed. At the same time, the memorycontroller 31 causes an image sensor 6 to start photoelectricconversion, and causes an image processing circuit 54 to generate animage by using an image capturing signal read out from the image sensor6. Upon finishing driving the shutter 5, the MPU 30 drives the chargemotor (not shown) via the shutter driving circuit 39 to set the shutter5 in a charged state so as to prepare for the next shooting operation.The MPU 30 controls a mirror motor (not shown) via the motor drivingcircuit 38 to make the main mirror 4 and the sub-mirror 7 pivot from theup position to the down position, and terminates the series of shootingoperations.

In step S309, the MPU 30 determines whether the user has selected afocus calibration mode. If YES in step S309, the process advances tostep S310. If NO in step S309, the process advances to step S311. Instep S310, the MPU 30 executes the selected focus calibration mode. Thisoperation will be described in detail later.

In step S311, the MPU 30 determines whether the user has turned off thepower supply by operating the power button 48. If YES in step S311, theMPU 30 terminates the camera operation. If NO in step S311, the processreturns to step S301 to continue the camera operation.

In step S312, the MPU 30 starts live view display upon selection of TVAFin step S301. More specifically, the MPU 30 controls the mirror motor(not shown) via the motor driving circuit 38 to make the main mirror 4and the sub-mirror 7 pivot to the up position and retract outside theimaging optical path. The MPU 30 also drives the charge motor (notshown) via the shutter driving circuit 39 to set the shutter 5 in anopen state as shown in FIG. 2. The memory controller 31 then causes theimage sensor 6 to start photoelectric conversion, and causes a liquidcrystal monitor 14 to display a live view image which is the movingimage generated by the image processing circuit 54 using the imagecapturing signal read out from the image sensor 6. The user then setsthe position of a TVAF frame 300 displayed on the liquid crystal monitor14, and selects an object.

In step S313, the MPU 30 determines whether the user has half-pressedthe release button 43 to turn on the first switch SW1. If YES in stepS313, the position of the TVAF frame 300 is confirmed, and the processadvances to step S303. If NO in step S313, the process waits until thefirst switch SW1 is turned on.

In step S314, the MPU 30 drives the focus motor 15 via the lens controlcircuit 33 to start driving the focus lens 3 a in increments of apredetermined amount.

In step S315, the contrast in-focus position of the focus lens 3 a isdetected by the contrast detection method. More specifically, first ofall, the memory controller 31 generates a contrast evaluation image byreading out an image capturing signal in the TVAF frame 300 from theimage sensor 6, and temporarily records the image in the SDRAM 53. Thememory controller 31 determines whether a peak image is obtained. If apeak image can be detected, the process advances to step S316. If nopeak image can be detected, a peak image is repeatedly detected at eachposition set by driving the focus lens 3 a by a predetermined amount.Since a peak image cannot be detected without acquiring at least threecontrast evaluation images, step S315 is repeated at least three times.

In step S316, the MPU 30 stops the focus motor 15 via the lens controlcircuit 33 to finish driving the focus lens 3 a.

In step S317, the MPU 30 determines whether the user has fully pressedthe release button 43 to turn on the second switch SW2. If YES in stepS317, the process advances to step S318. If NO in step S317, the processwaits until the second switch SW2 is turned on.

In step S318, the memory controller 31 causes the image sensor 6 tostart photoelectric conversion, and causes the image processing circuit54 to generate an image by using the image capturing signal read outfrom the image sensor 6.

In step S319, it is determined whether a distance measurement pointoverlapping the position of the TVAF frame 300 having undergone contrastfocusing and a CAL correction amount for a distance measurement pointarranged near the distance measurement point are recorded in the EEPROM32. If no CAL correction amount is recorded, the process advances tostep S320 to execute an automatic focus calibration function for thedistance measurement point. If a CAL correction amount is recorded, theprocess advances to step S325. In this case, a CAL correction amount ischecked at a specific distance measurement point. However, thisoperation may be formed for all the distance measurement points.

In step S320, the MPU 30 finishes the live view display. Morespecifically, the MPU 30 controls the mirror motor (not shown) via themotor driving circuit 38 to make the main mirror 4 and the sub-mirror 7pivot to the down position shown in FIG. 1.

In step S321, the MPU 30 performs focus detection by the phasedifference detection method via the focus detection circuit 36 withrespect to a distance measurement point subjected to automatic focuscalibration, and calculates a phase difference in-focus position basedon the detection result. The MPU 30 then temporarily records theposition in the SDRAM 53.

In step S322, the MPU 30 calculates the difference between the contrastin-focus position obtained in step S315 and the phase differencein-focus position of the distance measurement point obtained in stepS321. This difference is a CAL correction amount for the phasedifference in-focus position of the focus calibration possible distancemeasurement point.

In step S323, the MPU 30 records the calculated CAL correction amountfor the distance measurement point in the EEPROM 32. In step S324, an AFframe 800 corresponding to the distance measurement point for which theCAL correction amount is recorded is displayed, and an automatic focuscalibration result is displayed on the liquid crystal monitor 14. Inthis case, it is possible to use any display method which allows theuser to visually recognize the automatic focus calibration result.

In step S325, it is determined whether the user has finished the liveview display. If the user has performed the operation to finish thedisplay, the process advances to step S309. If the user has notperformed the operation, the process moves to step S313 to continue thelive view display.

The flowchart of FIG. 13 shows an operation performed in a detailedcalibration mode of performing focus calibration. The detailedcalibration mode is a mode of performing focus calibration with respectto all distance measurement points by repeating TVAF and phasedifference AF for each distance measurement point.

In step S401, the MPU 30 advances to step S402 when the user selects thedetailed calibration mode by operating the mode button 44 and theelectronic dial 45.

In step S402, the MPU 30 starts the counting operation of an operationtimer T for focus calibration. In this case, the operation timer T maybe automatically set in the camera or may be set in advance by the user.In step S403, 1 is set in a counter N for counting the 61 distancemeasurement points of an area sensor 8 d.

In step S404, it is determined whether a CAL correction amount for theNth distance measurement point is recorded in the EEPROM 32. If YES instep S404, the process advances to step S405. If NO in step S404, theprocess advances to step S406. In this case, it is determined that focuscalibration is not to be performed again with respect to each distancemeasurement point for which a CAL correction amount is recorded uponexecution of the automatic focus calibration function in steps S319 toS324. In step S405, the MPU 30 adds 1 to the counter N, and repeats thedetermination in step S404.

In step S406, the MPU 30 starts live view display to perform focuscalibration. More specifically, the MPU 30 controls a mirror motor (notshown) via the motor driving circuit 38 to make the main mirror 4 andthe sub-mirror 7 pivot to the up position and retract outside theimaging optical path. The MPU 30 also drives a charge motor (not shown)via the shutter driving circuit 39 to set the shutter 5 in an open stateas shown in FIG. 2. The memory controller 31 causes the image sensor 6to start photoelectric conversion, and causes the liquid crystal monitor14 to display a live view image which is the moving image generated bythe image processing circuit 54 using the image capturing signal readout from the image sensor 6. The user searches for an object subjectedto focus calibration while seeing this live view image, and arranges thecamera.

In step S407, the MPU 30 drives the focus motor 15 via the lens controlcircuit 33 to start driving the focus lens 3 a in increments of apredetermined amount. In step S408, the contrast in-focus position ofthe focus lens 3 a is detected by the contrast detection method. Morespecifically, first of all, the memory controller 31 generates acontrast evaluation image by reading out an image capturing signal inthe TVAF frame 300 from the image sensor 6, and temporarily records theimage in the SDRAM 53. The memory controller 31 determines whether apeak image has been obtained. If a peak image can be detected, theprocess advances to step S409. If no peak image can be obtained, a peakimage is repeatedly detected at each position set by driving the focuslens 3 a by a predetermined amount. Since a peak image cannot bedetected unless at least three contrast evaluation images are acquired,step S408 is repeated at least three times.

In step S409, the MPU 30 stops the focus motor 15 via the lens controlcircuit 33 to finish driving the focus lens 3 a. In step S410, the focuscalibration possibility determination routine is executed. This focuscalibration possibility determination routine is the same routine inFIG. 5, and a description of it will be omitted.

In step S411, the MPU 30 determines the focus calibration possibilitydetermination routine result at the Nth distance measurement point. Ifthe result indicates CAL_OK_FLAG, the process advances to step S412. Ifthe result indicates CAL_NG_FLAG, the process advances to step S416.

In step S412, the MPU 30 finishes the live view display. Morespecifically, the MPU 30 controls the mirror motor (not shown) via themotor driving circuit 38 to make the main mirror 4 and the sub-mirror 7pivot to the down position shown in FIG. 1.

In step S413, the MPU 30 performs focus detection by the phasedifference detection method via the focus detection circuit 36 withrespect to the Nth distance measurement point, and calculates a phasedifference in-focus position based on the detection result. The MPU 30then temporarily records the calculated position in the SDRAM 53.

In step S414, the MPU 30 calculates the difference between the contrastin-focus position obtained in step S408 and the phase differencein-focus position obtained in step S413. This difference is a CALcorrection amount corresponding to the phase difference in-focusposition of the Nth distance measurement point.

In step S415, the MPU 30 records the calculated CAL correction amountfor the Nth distance measurement point in the EEPROM 32. In step S416,the MPU 30 determines via a sensor (not shown) whether a camera 1 is seton a tripod. If YES in step S416, the process advances to step S418. IfNO in step S416, the process advances to step S417.

In step S417, it is determined whether the time set in an operationtimer T has elapsed. If YES in step S417, the process advances to stepS419. If NO in step S417, the process advances to step S418.

In step S418, it is determined whether focus calibration with respect tothe 61st distance measurement point is complete, that is, focuscalibration with respect to all the distance measurement points iscomplete. If YES in step S418, the process advances to step S419. If NOin step S418, the process advances to step S405.

In step S419, when focus calibration with respect to all the distancemeasurement points is complete or the operation timer T for focuscalibration has timed out, the focus calibration result is displayed onthe liquid crystal monitor 14. As this display method, any displaymethod can be used as long as it allows the user to visually recognizethe result. When the display is complete, the process returns to stepS311.

As described above, according to this embodiment, it is possible toinhibit the execution of focus calibration with respect to a distancemeasurement point for which a CAL correction amount is set by automaticfocus calibration. In addition, if focus calibration takes much timebecause of a large number of distance measurement points, it is possibleto perform focus calibration only within a preset time. In addition, ifa tripod is used, it is possible to perform focus calibration withrespect to all the distance measurement points even within a presettime. This allows the user to easily and efficiently perform focuscalibration.

This embodiment is configured to neglect the operation timer T whenusing a tripod. However, the operation time may be prolonged.Furthermore, the user may set the operation time. Although the operationof focus calibration is limited by the preset time of the operationtimer T, the operation may be limited by the camera shake amountdetected by an acceleration sensor (not shown) within the camera or thelens. For example, it may be determined, by threshold processing forshake amounts, that focus calibration is to be continued. Alternatively,if the shake amount is small, the operation timer T for time limit maybe prolonged. Furthermore, if a large shake amount is measured, focuscalibration may be stopped.

Fourth Embodiment

The operation of the digital single-lens reflex camera according to thisembodiment will be described with reference to the flowcharts shown inFIGS. 14 and 5. The flowchart of FIG. 14 shows an operation performed inthe normal calibration mode of performing focus calibration. The normalcalibration mode is a mode of simultaneously performing focuscalibration with respect to a plurality of distance measurement pointsat a given position of a focus lens 3 a. The arrangements of the camerabody and the interchangeable lens according to this embodiment are thesame as those in the first embodiment, and the same reference numeralsas those in the first embodiment denote constituent elements common tothose of the first embodiment. An MPU 30 and a memory controller 31,both of which are computers, execute the operations shown in FIGS. 14and 5 in accordance with computer programs.

In step S1101, the MPU 30 advances to step S1102 when the user selectsthe normal calibration mode by operating a mode button 44 and anelectronic dial 45.

In step S1102, the MPU 30 causes a liquid crystal monitor 14 to displaywhether to shift to a mode in which it is possible to discriminate, bychanging the AF frame display at a phase difference AF distancemeasurement point, whether a proper focus correction amount has beenobtained by focus calibration. When performing an operation in thenormal focus calibration mode, the process advances to step S1110.

In this case, the displayed state of focus calibration possibilitydetermination results on the liquid crystal monitor 14 is the same asthat shown in FIG. 7 in the first embodiment.

FIG. 15 shows a display 180 on the liquid crystal monitor 14 when makinga shift to a mode of individually setting AF frame (803, 831, 859, andthe like) display after the execution of calibration based on focuscalibration possibility determination results.

Upon determining in step S1103 that an identification display of a phasedifference AF distance measurement point in the mode in step S1102 is tobe selected from the data set and stored in the image capturingapparatus in advance, the MPU 30 advances to step S1104. Upondetermining that a distance measurement point display identificationmethod is to be newly customized and set, the process advances to stepS1105.

Referring to FIG. 16, when selecting an AF frame (800) display at thetime of focus calibration possibility determination from the data storedin the MPU 30 of the digital single-lens reflex camera, the user selects“Yes” 181. When newly setting an AF frame (800) display after focuscalibration possibility determination, the user selects “No” 185.

In step S1104, an AF frame display (803, 831, 859, and the like) set orselected by the user at the time of focus calibration is temporarilystored in the MPU 30 of the digital single-lens reflex camera. FIG. 17shows a display on the liquid crystal monitor 14 before the start of LVafter the setting of an AF frame (800) display at the time of focuscalibration.

In step S1105, a setting is made to determine whether to specify thenumber of times of focus calibration.

FIG. 18 shows a display on the liquid crystal monitor 14 when settingthe number of times of execution of focus calibration. The user sets thenumber of times from a count selection display 183 by operating theelectronic dial 45 or a multi-controller 46 or touch-operating theliquid crystal monitor 14.

In step S1106, when making a setting to perform focus calibration aplurality of times, a display method for phase difference distancemeasurement points processed until a focus correction value is stored isset.

FIG. 19 shows a screen for selecting a display setting for an AF frame(800), for which the focus calibration determination result indicates OKor from which a proper focus correction value is obtained, by operatingthe electronic dial 45 or the multi-controller 46 or touch-operating theliquid crystal monitor 14.

In step S1107, in the setting of performing focus calibration aplurality of times, a display method is set for each phase differencedistance measurement point from which a proper focus correction valuecould not be obtained.

FIG. 20 shows a screen for selecting a display setting for an AF frame(800), for which the focus calibration determination result indicatesNG, by operating the electronic dial 45 or the multi-controller 46 ortouch-operating the liquid crystal monitor 14.

In step S1108, a setting is made to determine whether to limit distancemeasurement points subjected to focus calibration.

FIG. 21 shows a screen for selecting a display setting for AF frame(800) when distance measurement points subjected to focus calibrationare limited and determination results indicate OK, by operating theelectronic dial 45 or the multi-controller 46 or touch-operating theliquid crystal monitor 14. For example, selected distance measurementpoints 184 are displayed differently from unselected distancemeasurement points. In addition, when distance measurement pointssubjected to focus calibration are not limited, “ALL” 186 is selected.Upon completing the selection of distance measurement points, “OK” 181is selected.

In step S1109, a PN liquid crystal panel 12 displays information for theconfirmation of AF frame display settings to confirm the settings madein steps S1105 to S1108.

FIG. 22 shows a screen displayed on the liquid crystal monitor 14 toconfirm the display setting contents of AF frames (800) when anindividual distance measurement point identification display is set atthe time of focus calibration.

In step S1110, the MPU 30 starts LV (live view) display to perform focuscalibration. More specifically, the MPU 30 controls a mirror motor (notshown) via a motor driving circuit 38 to make a main mirror 4 and asub-mirror 7 pivot to the up position and retract outside the imagingoptical path. In addition, the MPU 30 drives a charge motor (not shown)via a shutter driving circuit 39 to set a shutter 5 in an open state asshown in FIG. 2. The memory controller 31 then causes an image sensor 6to start photoelectric conversion (electric charge accumulation andelectric charge readout), and causes the liquid crystal monitor 14 todisplay a live view image which is the moving image generated by animage processing circuit 54 using the image capturing signal read outfrom the image sensor 6. The user searches for an object for focuscalibration while seeing this live view image, and arranges the camera.

Although described in the first embodiment, FIG. 6 is a view showing thedisplay state of the liquid crystal monitor 14 in the live view mode.The liquid crystal monitor 14 is displaying a traffic sign 200 which isan object as a live view image. A TVAF frame 300 is displayed in thecenter of the imaging screen. Although the TVAF frame 300 is arranged inthe center of the imaging screen in FIG. 6, the TVAF frame 300 may bearranged at any position on the imaging screen.

In step S1111, the MPU 30 determines whether the user has half-pressed arelease button 43 to turn on a first switch SW1. If YES in step S1111,an object subjected to focus calibration is confirmed. The process thenadvances to step S1112. If NO in step S1111, the process waits until thefirst switch SW1 is turned on.

In step S1112, the MPU 30 drives the focus motor 15 via the lens controlcircuit 33 to start driving the focus lens 3 a in increments of apredetermined amount. In step S1113, the contrast in-focus position ofthe focus lens 3 a is detected by the contrast detection method. Morespecifically, first of all, the memory controller 31 reads out an imagecapturing signal in the TVAF frame 300 from the image sensor 6, andgenerates a contrast evaluation image. The memory controller 31 thentemporarily records the signal in an SDRAM 53. The memory controller 31determines whether an image exhibiting maximum (peak) contrast (to bereferred to as a peak image hereinafter) has been obtained. If a peakimage can be detected, the process advances to step S1114. If a peakimage cannot be detected, a peak image is repeatedly detected at aposition to which the focus lens 3 a is driven by a predeterminedamount. Since a peak image cannot be detected unless at least threecontrast evaluation images are acquired, step S1113 is repeated at leastthree times.

In step S1114, the MPU 30 stops the focus motor 15 via the lens controlcircuit 33 to finish driving the focus lens 3 a. At this time point, thefocus lens 3 a is at rest at a position (contrast in-focus position)where the traffic sign 200 as an object subjected to focus calibrationis in focus.

In step S1115, 1 is set in a counter N for counting 61 distancemeasurement points of an area sensor 8 d. In step S1116, the focuscalibration possibility determination routine is executed. A detailedoperation in this routine will be described later.

In step S1117, it is determined whether the focus calibrationpossibility determination routine has been executed with respect to the61st distance measurement point, that is, has been completed withrespect to all the distance measurement points. If YES in step S1117,the process advances to step S1119. If NO in step S1117, the processadvances to step S1118. In step S1118, 1 is added to the counter N, andstep S1116 is repeated.

In step S1119, the memory controller 31 displays, on the liquid crystalmonitor 14, focus calibration possibility determination results on AFdistance measurement frames corresponding to the area sensor 8 d incorrespondence with the phase difference AF frames set in steps S1106and S1107. The focus calibration possibility determination results canbe discriminated by CAL_OK_FLAG or CAL_NG_FLAG temporarily recorded inthe SDRAM 53 in the focus calibration possibility determination routinedescribed later.

Although described in the first embodiment, FIG. 7 shows a state inwhich focus calibration possibility determination results are displayedon the liquid crystal monitor 14. AF frames 800 indicating 61 distancemeasurement points of the area sensor 8 d are displayed. The individualnumbers of the AF frames 800 are counted from the left end to the rightend, and from the upper side to the lower side, starting from an AFframe 801 on the upper left, with the central frame being an AF frame831 and the lower right frame being an AF frame 861. Therefore, thefirst distance measurement point of the counter N corresponds to an AFframe 801, and the 61st distance measurement point corresponds to an AFframe 861. In addition, a CAL start button 310 and a cancel button 320are displayed.

AF frames indicating distance measurement points where focus calibrationcan be performed are displayed in solid lines (801, 804, 814, 848, 858,861, and the like). AF frames indicating distance measurement pointswhere focus calibration cannot be performed are displayed in dottedlines (803, 831, 859, and the like). In the case shown in FIG. 7, thefocus calibration possibilities of the respective distance measurementpoints are indicated by the solid and dotted lines of AF frames.

In step S1120, the MPU 30 determines whether the user has turned on aCAL start button 310. More specifically, if the user operates a SETbutton 47 upon selecting the CAL start button 310 by operating theelectronic dial 45 or the multi-controller 46, the CAL start button isturned on, and the process advances to step S1121. If the CAL startbutton 310 is not turned on (that is, a cancel button 320 is turned on),the focus calibration mode is finished.

In step S1121, the live view display is finished. More specifically, theMPU 30 controls the mirror motor (not shown) via the motor drivingcircuit 38 to make the main mirror 4 and the sub-mirror 7 pivot to thedown position shown in FIG. 1.

In step S1122, the MPU 30 performs focus detection by the phasedifference detection method via the focus detection circuit 36 withrespect to a distance measurement point determined as a focuscalibration possible distance measurement point, calculates a phasedifference in-focus position based on the result, and temporarilyrecords the position in the SDRAM 53.

In step S1123, the MPU 30 calculates the difference between the contrastin-focus position obtained in step S1105 and the phase differencein-focus position of the focus calibration possible distance measurementpoint obtained in step S1122. This difference is a correction amount (tobe referred to as a CAL correction amount hereinafter) for the phasedifference in-focus position of the focus calibration possible distancemeasurement point. In step S1124, the MPU 30 stores the calculated CALcorrection amount for the focus calibration possible distancemeasurement point in the EEPROM 32.

In step S1125, if the number of times of execution of focus calibrationis less than the number of times set in step S1105, the process returnsto step S1110 to continuously start LV. If the number of times ofexecution of focus calibration exceeds the number of times set in stepS1105 or the operation is to be forcibly terminated, the calibrationoperation is terminated.

The flowchart of FIG. 5 shows an operation performed in the focuscalibration possibility determination routine at all the distancemeasurement points. This operation has already been described in thefirst embodiment, and hence a description of it will be omitted.

FIG. 23 is a view showing, as a thick solid line AF frame 872, eachdistance measurement point for which it is determined that focuscalibration can be performed, and also showing, as a solid line AF frame870, each distance measurement point for which it is determined thatfocus calibration cannot be performed, when the first focus calibrationpossibility determination is executed based on the same situation asthat described with reference to FIG. 7 and a contrast determinationcriterion in the digital single-lens reflex camera in which all 61distance measurement points are arranged. If OK is determined in thisstate, when the user selects the CAL start button 310, the first focuscalibration starts. If NG is determined, the user selects the cancelbutton 320. The user checks the number of times of focus calibration ona display 330.

FIG. 24 is a view showing, as a dotted line AF frame 871, each distancemeasurement point for which the processing has been completed up to thestorage of a focus correction value, and also showing, as a solid lineAF frame 870, each distance measurement point for which no focuscorrection value has been acquired, when the first focus calibration iscomplete. Subsequently, in order to perform the second focuscalibration, the digital single-lens reflex camera is moved so as tomake the solid line AF frame 870 intersect with an edge line of thetraffic sign 200. The user then selects the CAL start button 310 tostart the second focus calibration at the positions of the traffic sign200 and the AF frame shown in FIG. 25.

FIG. 25 is a view showing, as a dotted line AF frame 871, each distancemeasurement point for which the processing has been completed up to thestorage of a focus correction value, and also showing, as a solid lineAF frame 870, each distance measurement point for which no focuscorrection value has been acquired, when the second focus calibration isexecuted. In order to perform the third focus calibration with respectto the solid line AF frames 870, the positions of the traffic sign 200and each AF frame are changed in the same manner as described above toset a positional relationship like that shown in FIG. 26.

FIG. 26 is a view showing, as a dotted line AF frame 871, each distancemeasurement point for which the processing has been completed up to thestorage of a focus correction value, and also showing, as a solid lineAF frame 870, each distance measurement point for which no focuscorrection value has been acquired, when the third focus calibration isexecuted. In order to perform the fourth focus calibration with respectto the solid line AF frames 870, the positions of the traffic sign 200and each AF frame are changed in the same manner as described above toset a positional relationship like that shown in FIG. 27.

Referring to FIG. 27, all the distance measurement points have undergonethe processing up to the storage of focus correction values and becomedotted line AF frames 871. Therefore, the user selects a CAL end button340 to terminate the focus calibration.

As has been described above, according to this embodiment, it isdetermined by using an image capturing signal from the image sensor 6whether it is possible to perform focus calibration with respect to theobject selected by the user. This makes it possible to easily identify,based on focus calibration accuracy differences, distance measurementpoints, of a plurality of phase difference AF distance measurementpoints, for which proper focus correction values have been acquired orhave not been acquired. This can prevent any wasteful correctingoperation. Therefore, the user can easily and efficiently perform focuscalibration without using any dedicated chart.

The preferred embodiments of the present invention have been describedabove. However, the present invention is not limited to theseembodiments, and can be variously changed and modified within the spiritand scope of the invention.

Other Embodiments

Embodiment(s) of the present invention can also be realized by acomputer of a system or apparatus that reads out and executes computerexecutable instructions (e.g., one or more programs) recorded on astorage medium (which may also be referred to more fully as a‘non-transitory computer-readable storage medium’) to perform thefunctions of one or more of the above-described embodiment(s) and/orthat includes one or more circuits (e.g., application specificintegrated circuit (ASIC)) for performing the functions of one or moreof the above-described embodiment(s), and by a method performed by thecomputer of the system or apparatus by, for example, reading out andexecuting the computer executable instructions from the storage mediumto perform the functions of one or more of the above-describedembodiment(s) and/or controlling the one or more circuits to perform thefunctions of one or more of the above-described embodiment(s). Thecomputer may comprise one or more processors (e.g., central processingunit (CPU), micro processing unit (MPU)) and may include a network ofseparate computers or separate processors to read out and execute thecomputer executable instructions. The computer executable instructionsmay be provided to the computer, for example, from a network or thestorage medium. The storage medium may include, for example, one or moreof a hard disk, a random-access memory (RAM), a read only memory (ROM),a storage of distributed computing systems, an optical disk (such as acompact disc (CD), digital versatile disc (DVD), or Blu-ray Disc (BD)™),a flash memory device, a memory card, and the like.

While the present invention has been described with reference toexemplary embodiments, it is to be understood that the invention is notlimited to the disclosed exemplary embodiments. The scope of thefollowing claims is to be accorded the broadest interpretation so as toencompass all such modifications and equivalent structures andfunctions.

This application claims the benefit of Japanese Patent Application No.2013-235386, filed Nov. 13, 2013, which is hereby incorporated byreference herein in its entirety.

What is claimed is:
 1. An image capturing apparatus comprising: animaging unit configured to generate an imaging signal byphotoelectrically converting an object image formed by an imagingoptical system including a focus lens; a sensor unit including aplurality of pairs of sensors each of which generate a pair of imagesignals by photoelectrically converting an object image formed by theimaging optical system in correspondence with each of a plurality offocus detection areas; a first focus detection unit configured to detecta first in-focus position based on the pair of image signals generatedby said sensor unit; a second focus detection unit configured to detecta second in-focus position based on a signal output from said imagingunit; a control unit configured to control a position of the focus lensand control display indicating the focus detection areas; an acquisitionunit configured to acquire a correction amount based on a differencebetween the first in-focus position and the second in-focus position andstore the correction amount in a memory in a correction mode; and acorrection unit configured to correct the first in-focus position at thetime of imaging based on the correction amount stored in the memory,wherein in the correction mode, said acquisition unit determines a firstfocus detection area, among the plurality of focus detection areas, fromwhich the correction amount is configured to be acquired after the focuslens is moved to the second in-focus position by said control unit, andsaid control unit controls display indicating the first focus detectionarea determined by said acquisition unit to be identifiable.
 2. Theapparatus according to claim 1, wherein said acquisition unit acquiresthe correction amount with respect to the first focus detection areaafter the control unit controls display indicating the first focusdetection area to be identifiable.
 3. The apparatus according to claim1, wherein in the correction mode, said first focus detection unitcalculates the first in-focus position based on the pair of imagesignals generated from the pair of sensors corresponding to the firstfocus detection area, and said acquisition unit acquires the correctionamount based on a difference between the calculated first in-focusposition and the second in-focus position.
 4. The apparatus according toclaim 1, wherein when there are the plurality of first focus detectionareas, said acquisition unit acquires and stores the correction amountfor each of the first focus detection areas.
 5. The apparatus accordingto claim 1, wherein said control unit controls display indicating thefirst focus detection area to be a different form from displayindicating the other focus detection area.
 6. The apparatus according toclaim 1, wherein said acquisition unit determines the first focusdetection area from which the correction amount is configured to beacquired, based on at least one of a contrast, luminance, conflict ofperspective, repetitive pattern, and color of an object image, by usingthe imaging signal or a photometric signal used for exposure control. 7.The apparatus according to claim 1, wherein said second focus detectionunit detects the second in-focus position by a contrast detection methodbased on the imaging signal.
 8. The apparatus according to claim 7,wherein said second focus detection unit detects the second in-focusposition based on the imaging signal corresponding to a predeterminedarea in a screen.
 9. The apparatus according to claim 1, wherein saidcontrol unit receives an operation to instruct whether to acquire thecorrection amount while the control unit controls display indicating thefirst focus detection area to be identifiable.
 10. The apparatusaccording to claim 9, wherein when the operation to instruct to acquirethe correction amount is performed, said acquisition unit acquires thecorrection amount with respect to the first focus detection area. 11.The apparatus according to claim 9, wherein when the operation to stopacquiring the correction amount is performed, said acquisition unitstops acquiring the correction amount.
 12. A method of controlling animage capturing apparatus including an imaging unit configured togenerate an imaging signal by photoelectrically converting an objectimage formed by an imaging optical system including a focus lens, and asensor unit including a plurality of pairs of sensors each of whichgenerate a pair of image signals by photoelectrically converting anobject image formed by the imaging optical system in correspondence witheach of a plurality of focus detection areas, the method comprising: afirst focus detection step of detecting a first in-focus position basedon the pair of image signals generated by the sensor unit; a secondfocus detection step of detecting a second in-focus position based on asignal output from the imaging unit; a focus control step of controllinga position of the focus lens; a display control step of controllingdisplay indicating the focus detection areas; an acquisition step ofacquiring a correction amount based on a difference between the firstin-focus position and the second in-focus position in a correction mode;a storing step of storing the correction amount in a memory in thecorrection mode; and a correction step of correcting the first in-focusposition at the time of imaging based on the correction amount stored inthe memory, wherein in the correction mode, after the focus lens ismoved to the second in-focus position in the focus control step, a firstfocus detection area, among the plurality of focus detection areas, fromwhich the correction amount is configured to be acquired is determinedin the acquisition step, and in the display control step, displayindicating the first focus detection area determined in the acquisitionstep is controlled to be identifiable.
 13. A non-transitorycomputer-readable recording medium storing a program for causing acomputer to execute each step in a method of controlling an imagecapturing apparatus including an imaging unit configured to generate animaging signal by photoelectrically converting an object image formed byan imaging optical system including a focus lens, and a sensor unitincluding a plurality of pairs of sensors each of which generate a pairof image signals by photoelectrically converting an object image formedby the imaging optical system in correspondence with each of a pluralityof focus detection areas, the method comprising: a first focus detectionstep of detecting a first in-focus position based on the pair of imagesignals generated by the sensor unit; a second focus detection step ofdetecting a second in-focus position based on a signal output from theimaging unit; a focus control step of controlling a position of thefocus lens; a display control step of controlling display indicating thefocus detection areas; an acquisition step of acquiring a correctionamount based on a difference between the first in-focus position and thesecond in-focus position in a correction mode; a storing step of storingthe correction amount in a memory in the correction mode; and acorrection step of correcting the first in-focus position at the time ofimaging based on the correction amount stored in the memory, wherein inthe correction mode, after the focus lens is moved to the secondin-focus position in the focus control step, a first focus detectionarea, among the plurality of focus detection areas, from which thecorrection amount is configured to be acquired is determined in theacquisition step, and in the display control step, display indicatingthe first focus detection area determined in the acquisition step iscontrolled to be identifiable.
 14. An image capturing apparatuscomprising: an image sensor configured to generate an imaging signal byphotoelectrically converting an object image formed by an imagingoptical system including a focus lens; a sensor component including aplurality of pairs of sensors each of which generate a pair of imagesignals by photoelectrically converting an object image formed by theimaging optical system in correspondence with each of a plurality offocus detection areas; and one or more processors configured to functionas: a first focus detection unit configured to detect a first in-focusposition based on the pair of image signals generated by said sensorcomponent; a second focus detection unit configured to detect a secondin-focus position based on a signal output from said image sensor; acontrol unit configured to control a position of the focus lens andcontrol display indicating the focus detection areas; an acquisitionunit configured to acquire a correction amount based on a differencebetween the first in-focus position and the second in-focus position andstore the correction amount in a memory in a correction mode; and acorrection unit configured to correct the first in-focus position at thetime of imaging based on the correction amount stored in the memory,wherein in the correction mode, said acquisition unit determines a firstfocus detection area, among the plurality of focus detection areas, fromwhich the correction amount is configured to be acquired after the focuslens is moved to the second in-focus position by said control unit, andsaid control unit controls display indicating the first focus detectionarea determined by said acquisition unit to be identifiable.
 15. Theapparatus according to claim 14, wherein said acquisition unit acquiresthe correction amount with respect to the first focus detection areaafter the control unit controls display indicating the first focusdetection area to be identifiable.
 16. The apparatus according to claim14, wherein in the correction mode, said first focus detection unitcalculates the first in-focus position based on the pair of imagesignals generated from the pair of sensors corresponding to the firstfocus detection area, and said acquisition unit acquires the correctionamount based on a difference between the calculated first in-focusposition and the second in-focus position.
 17. The apparatus accordingto claim 14, wherein when there are the plurality of first focusdetection areas, said acquisition unit acquires and stores thecorrection amount for each of the first focus detection areas.
 18. Theapparatus according to claim 14, wherein said control unit controlsdisplay indicating the first focus detection area to be a different formfrom display indicating the other focus detection area.
 19. Theapparatus according to claim 14, wherein said acquisition unitdetermines the first focus detection area from which the correctionamount is configured to be acquired, based on at least one of acontrast, luminance, conflict of perspective, repetitive pattern, andcolor of an object image, by using the imaging signal or a photometricsignal used for exposure control.
 20. The apparatus according to claim14, wherein said second focus detection unit detects the second in-focusposition by a contrast detection method based on the imaging signal. 21.The apparatus according to claim 20, wherein said second focus detectionunit detects the second in-focus position based on the imaging signalcorresponding to a predetermined area in a screen.
 22. The apparatusaccording to claim 14, wherein said control unit receives an operationto instruct whether to acquire the correction amount while the controlunit controls display indicating the first focus detection area to beidentifiable.
 23. The apparatus according to claim 22, wherein when theoperation to instruct to acquire the correction amount is performed,said acquisition unit acquires the correction amount with respect to thefirst focus detection area.
 24. The apparatus according to claim 22,wherein when the operation to stop acquiring the correction amount isperformed, said acquisition unit stops acquiring the correction amount.